Heretofore resistance welding (e.g. spot welding) and arc welding utilizing an electric energy have been conducted in a wide range of industrial fields and are both currently important, indispensable techniques in industries.
Resistance welding, typically spot welding, entails the most serious problem of forming a film of oxide on oxidation of the parts of a steel plate or the like to be welded or neighboring parts due to the intensive heat given off during welding. The oxide film or scale is usually in the form of a brown ring and responsible for deteriorated appearance of articles and possibly for impaired functions of articles. Such scales have been removed by means of at least one of procedures such as acid washing, electrolysis, polishing, sandblasting and the like. However, these techniques have the drawbacks of e.g., marring the base-metal surfaces and involving time-consuming labor.
Attempts have been made to prevent scales from forming in order to obviate the foregoing problems. For example, the metal parts to be welded have been shielded with an non-oxidizing gas. The method, however, is expensive but unsatisfactory in the result. Another proposed method is to apply a coating of oil, resin or the like on the parts to be welded or adjacent parts to form a barrier film against the oxygen in the atmosphere. The method is also ineffective and disadvantageous in that the coating hinders welding and that the adhered coating is difficult to remove.
We developed a composition for preventing the scaling in resistance welding which composition contains as the active component a water-soluble silicone represented by a specific chemical formula (Japanese Unexamined Patent Publication No. 299865/1988). Yet the proposed composition is occasionally unable to prevent the scaling under severe welding conditions although able to produce good results under normal welding conditions.
Arc welding such as TIG or MIG arc welding poses the problem of producing scales on oxidation of the joint to be welded or adjacent parts (about 1 cm in width in the vicinity of the bead in TIG arc welding) due to the intensive heat (momentarily about 900.degree. C.) given off during welding (although on different principles of heat generation). Efforts have been made in this case to remove the scales by the same methods as employed in resistance welding and to inhibit the formation of scales by methods identical with or close to those done in resistance welding, using a scale-preventing agent, but without satisfactory result.